Prosthesis system including tibial bearing component

ABSTRACT

According to one example, a tibial bearing component for articulation with a medial condyle and a lateral condyle of a femoral component in a knee replacement procedure is disclosed. The tibial bearing component can include a distal surface and an articular surface opposing the distal surface. The articular surface can include a medial compartment and a lateral compartment configured for articulation with the medial condyle and the lateral condyle of the femoral component, respectively. The lateral compartment can have a lateral articular track with a lateral anterior-posterior extent. The lateral articular track can comprise a plurality of distal-most points along a proximal surface of the lateral compartment that are contacted by the lateral condyle during rollback of the femoral component. The medial compartment can differ in configuration from the lateral compartment and can have an anterior lip height of between about 9 mm and about 13 mm.

CLAIM OF PRIORITY

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/221,461, filed on Sep. 21, 2015, and also claimsthe benefit of U.S. Provisional Patent Application Ser. No. 62/309,046,filed on Mar. 16, 2016, the benefit of priority of each of which isclaimed hereby, and each of which are incorporated by reference hereinin its entirety.

FIELD

The present subject matter relates to orthopedic procedures and, moreparticularly, to prostheses, systems and methods used in kneearthroplasties.

BACKGROUND

Orthopedic procedures and prostheses are commonly utilized to repairand/or replace damaged bone and tissue in the human body. For example, aknee arthroplasty can be used to restore natural knee function byrepairing damaged or diseased articular surfaces of the femur and/ortibia. An incision is made into the knee joint to expose the bonescomprising the joint. Cut guides are used to guide the removal of thearticular surfaces that are to be replaced. Prostheses are used toreplicate the articular surfaces. Knee prostheses can include a femoralcomponent implanted on the distal end of the femur, which articulateswith a tibial bearing component and a tibial component implanted on theproximal end of a tibia to replicate the function of a healthy naturalknee. Various types of arthroplasties are known including a total kneearthroplasty, where all of the articulating compartments of the jointare repaired with prosthetic components.

OVERVIEW

This disclosure pertains generally to provisional tibial prostheses,systems, and methods. The present inventors have recognized, among otherthings that for knee prostheses, such as in a total knee arthroplasty, amedial condyle of the femoral component can experience lessanterior-posterior translation relative to the lateral condyle duringflexion of the knee joint. This can result in external rotation and amedial pivoting motion for the femoral component during femoralrollback. Considering these kinematics, the present inventors havedesigned tibial implants with medial and lateral compartments that canaccommodate such motions of the femoral component in a more desirablefashion. Thus, the present inventors propose a medial compartment forthe tibial bearing component that can be configured to provide a highdegree of conformity and constraint with the medial condyle of thefemoral component, and a lateral compartment of the tibial bearingcomponent that can be shaped to facilitate external rollback of thelateral condyle of the femoral component in deep flexion.

Medial Stability

In view of the above, the present inventors have designed a family oftibial bearing components that can have at least eleven different stocksizes so as to achieve more compatible combinations when used with afamily of tibia components that can have at least nine different stocksizes and a family of femoral components that can have at least twelvedifferent stock sizes. Due to the number of components and the designedcompatibility between various sizes in the respective families, twentyfour combinations of the at least eleven different stock sizes of thefamily of tibial bearing components can be compatible for operable usewith the at least twelve different stock sizes of the family of femoralcomponents. More particularly, because of the designed compatibilitybetween so many different sizes of femoral components and tibial bearingcomponents, in a worst case scenario a conformity between the femoralcomponent and the tibial bearing component in extension can have at mosta congruency ratio of 1.1:1, and over half (54%) of the conformitiesbetween the various sizes of tibial bearing component and the varioussizes of femoral component can have a medial congruency ratio of 1:1.

The present inventors further recognize that by increasing theconformity between the medial condyle of the femoral component and themedial compartment of the tibial bearing component, greater medialstability of the medial condyle can be achieved with an increase incontact area. Thus, the inventors propose tibial bearing articularsurface constructions that can facilitate greater conformity (and hencelarger contact areas) and examples where compatible combinations ofdifferently sized femoral and tibial bearing components from respectivefamilies of components can be combined to achieve more desirable largercontact areas. Such examples can achieve an arrangement where a minimumof 31% of an overall surface area of the medial compartment can becontacted with the femoral component in 0° flexion, and a minimum of 13%of the overall surface area of the medial compartment can be contactedwith the femoral component in 45° flexion. According to furtherexamples, an arrangement where an average of 54% of an overall surfacearea of the medial compartment can be contacted with the femoralcomponent in 0° flexion and an average of 38% of the overall surfacearea of the medial compartment can be contacted with the femoralcomponent in 45° flexion. The present inventors also propose an anteriorlip height for the medial compartment of the tibial bearing component ofbetween 9 mm and 13 mm (depending on the size of the tibial bearingcomponents). This anterior lip height can provide for greater anteriorsubluxation resistance to provide greater constraint to the medialcondyle of the femoral component.

Lateral Mobility

To facilitate greater mobility of the lateral condyle of the femoralcomponent relative to the lateral compartment of the tibial bearingcomponent, the present inventors propose that a sagittal geometry of thelateral compartment of the tibial bearing component can be configured tohave two separate radii comprising an anterior radius and a posteriorradius. The posterior radius when viewed in a transverse plane arcsabout the dwell point (a point of inflection on the articular surfacewhere the articular surface has a deepest distal extent) of the medialcompartment to facilitate external rotation of the femoral component fordeep flexion. Additionally, in some examples the dwell point of thelateral condyle can be positioned to further facilitate rollback of thelateral condyle of the femoral component for deep flexion. Inparticular, for the family of differently sized tibial bearingcomponents with an anterior tibial slope of 0°, an anterior-posteriorlocation of the lateral dwell point as a percentage of the totalanterior-posterior extent of the tibial bearing component can be betweenabout 65% and about 69% of the total anterior-posterior extent asmeasured from an anterior most point of the tibial bearing component toa posterior most point.

To further illustrate the apparatuses and systems disclosed herein, thefollowing non-limiting examples are provided:

Example 1 is a tibial bearing component for articulation with a medialcondyle and a lateral condyle of a femoral component in a kneereplacement procedure, the tibial bearing component can include a distalsurface and an articular surface opposing the distal surface. Thearticular surface can include a medial compartment and a lateralcompartment configured for articulation with the medial condyle and thelateral condyle of the femoral component, respectively. The lateralcompartment can have a lateral articular track with a lateralanterior-posterior extent, the lateral articular track can comprise aplurality of distal-most points along a proximal surface of the lateralcompartment that are contacted by the lateral condyle during rollback ofthe femoral component. The medial compartment can differ inconfiguration from the lateral compartment and can have an anterior lipheight of between about 9 mm and about 13 mm.

In Example 2, the subject matter of Example 1 can optionally include thelateral compartment can have an anterior portion and a posteriorportion, the anterior portion can define the lateral articular track asa nominally straight line when projected onto a transverse plane of thetibial bearing component, the posterior portion can define the lateralarticular track with a curved line toward the medial compartment whenprojected onto the transverse plane of the tibial bearing component.

In Example 3, the subject matter of Example 2 can optionally includewherein the lateral compartment can have a first sagittal radius in theanterior portion and can have a second sagittal radius in the posteriorportion.

In Example 4, the subject matter of any one or more of Examples 1-3 canoptionally include the medial compartment has a medial articular trackwith a medial anterior-posterior extent that differs from the lateralanterior-posterior extent. The medial articular track can comprise aplurality of distal-most points along a proximal surface of the medialcompartment that are contacted by the medial femoral condyle duringrollback of the femoral component. The medial compartment can define themedial articular track as a nominally straight line when projected ontothe transverse plane of the bearing component and the medial articulartrack has a single sagittal radius.

In Example 5, the subject matter of Example 4 can optionally include themedial compartment can be configured to have a medial dwell point adistance between about 61% and about 66% of a total anterior-posteriorextent of the tibial bearing component as measured from an anterior mostpoint to a posterior most point of the tibial bearing component.

In Example 6, the subject matter of any one or more of Examples 1-4 canoptionally include the lateral compartment can be configured to have alateral dwell point a distance between about 65% and about 69% of atotal anterior-posterior extent of the tibial bearing component asmeasured from an anterior most point to a posterior most point of thetibial bearing component.

In Example 7, the subject matter of any one or more of Examples 1-6 canoptionally include the medial compartment can be configured relative tothe medial condyle to have between about 31% and about 63% of an overallsurface area thereof contacted by the medial condyle of the femoralcomponent with the femoral component in 0° flexion.

In Example 8, the subject matter of any one or more of Examples 1-6 canoptionally include the medial compartment can be configured to havebetween about a 1.1 congruence ratio and about a 1.1:1 congruence ratiowith the medial condyle, the congruence ratio can comprise a ratio ofthe similarity between a sagittal radius of the medial compartment and asagittal radius of the medial condyle.

Example 9 is a system for knee arthroplasty that can include a family offemoral components having at least twelve different stock sizes and afamily of tibial bearing components having at least eleven differentstock sizes. Each of the femoral components can include a medial condyleand a lateral condyle. Each of the tibial bearing components can includea distal surface and an articular surface opposing the distal surface.The articular surface can include a medial compartment and a lateralcompartment configured for articulation with the medial condyle and thelateral condyle of the femoral component, respectively. The family oftibial bearing components can be configured such that twenty fourcombinations of the at least eleven different stock sizes of the familyof tibial bearing components are compatible for operable use with the atleast twelve different stock sizes of the family of femoral componentsand at least nine different stock sizes of a family of tibialcomponents.

In Example 10, the subject matter of Example 9 can optionally includethe family of femoral components and the family of tibial bearingcomponents can be configured such that between about 31% and about 63%of an overall surface area of the medial compartment is contacted by themedial condyle of the femoral component with the femoral component in 0°flexion.

In Example 11, the subject matter of any one or more of Examples 9-10can optionally include the medial compartment can be configured to havebetween about a 1.1 congruence ratio and about a 1.1:1 congruence ratiowith the medial condyle, the congruence ratio can comprise a ratio ofthe similarity between a sagittal radius of the medial compartment and asagittal radius of the medial condyle.

In Example 12, the subject matter of any one or more of Examples 9-11can optionally include the medial compartment can be configured to havea medial dwell point a distance between about 61% and about 66% of atotal anterior-posterior extent of the tibial bearing component asmeasured from an anterior most point to a posterior most point of thetibial bearing component.

In Example 13, the subject matter of any one or more of Examples 9-12can optionally include ten of the at least twelve different stock sizesof the family of femoral components can be compatible for operable usewith ten of the at least eleven different stock sizes of the family oftibial bearing components.

In Example 14, the subject matter of any one or more of Examples 9-13can optionally include eight of the at least twelve different stocksizes of the family of femoral components can be compatible for operableuse with six of the at least eleven different stock sizes of the familyof tibial bearing components.

In Example 15, the subject matter of any one or more of Examples 9-14can optionally include nine out of the at least eleven different stocksizes of the family of tibial bearing components can be compatible withno more than two of the at least twelve stock sizes of the family offemoral components, and no more than four of the at least twelvedifferent stock sizes of the family of femoral components can becompatible for operable use with two of the at least eleven differentstock sizes of the tibial bearing components.

In Example 16, the subject matter of any one or more of Examples 9-15can optionally include the medial compartment can have an anterior lipheight of between about 9 mm and about 13 mm.

In Example 17, the subject matter of any one or more of Examples 9-16can optionally include the medial compartment has a medial articulartrack having a medial anterior-posterior extent that differs from alateral anterior-posterior extent. The medial articular track cancomprise a plurality of distal-most points along a proximal surface ofthe medial compartment that are contacted by the medial femoral condyleduring rollback of the femoral component. The medial compartment candefine the medial articular track as a nominally straight line whenprojected onto the transverse plane of the bearing component and themedial articular track has a single sagittal radius.

Example 18 is a tibial bearing component for articulation with a medialcondyle and a lateral condyle of a femoral component in a kneereplacement procedure, the tibial bearing component can include a distalsurface and an articular surface opposing the distal surface. Thearticular surface can include a medial compartment and a lateralcompartment configured for articulation with the medial condyle and thelateral condyle of the femoral component, respectively. The lateralcompartment can be configured to have a lateral dwell point a distancebetween about 65% and about 69% of a total anterior-posterior extent ofthe tibial bearing component as measured from an anterior most point toa posterior most point of the tibial bearing component.

In Example 19, the subject matter of Example 18 can optionally includethe medial compartment can differ in configuration from the lateralcompartment and can have an anterior lip height of between about 9 mmand about 13 mm.

In Example 20, the subject matter of any one or more of Examples 18-19can optionally include the lateral compartment has a lateral articulartrack with a lateral anterior-posterior extent. The lateral articulartrack can comprise a plurality of distal-most points along a proximalsurface of the lateral compartment that are contacted by the lateralcondyle during rollback of the femoral component. The lateralcompartment can have an anterior portion and a posterior portion, theanterior portion can define the lateral articular track as a nominallystraight line when projected onto a transverse plane of the tibialbearing component, the posterior portion can define the lateralarticular track with a curved line toward the medial compartment whenprojected onto the transverse plane of the tibial bearing component.

In Example 21, the subject matter of Example 20 can optionally includewherein the lateral compartment can have a first sagittal radius in theanterior portion and can have a second sagittal radius in the posteriorportion.

In Example 22, the apparatuses or method of any one or any combinationof Examples 1-21 can optionally be configured such that all elements oroptions recited are available to use or select from.

These and other examples and features of the present apparatuses andsystems will be set forth in part in the following Detailed Description.This Overview is intended to provide non-limiting examples of thepresent subject matter—it is not intended to provide an exclusive orexhaustive explanation. The Detailed Description below is included toprovide further information about the present apparatuses and systems.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralscan describe similar components in different views. Like numerals havingdifferent letter suffixes can represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various examples discussed in the presentdocument.

FIG. 1 shows a schematic view of a proximal end of a natural tibia, withnormal medial and lateral condyle motion in accordance with an exampleof the present application.

FIG. 2 shows a femoral component assembled with a tibial bearingcomponent in accordance with an example of the present application.

FIG. 2A shows a cross-section of the femoral component and the tibialbearing component of FIG. 2 in a coronal plane in accordance with anexample of the present application.

FIG. 3 illustrates laxity envelopes and allowable anterior-posteriortranslation of the femoral component of FIGS. 2 and 2A relative to thetibial bearing component of FIGS. 2 and 2A in accordance with an exampleof the present application.

FIGS. 4A to 4D shows plots of the laxity envelopes of FIG. 3 relative toa prior art system in accordance with an example of the presentapplication.

FIG. 5 is a plan view of a proximal surface of a tibial bearingcomponent including features such as a medial compartment and a lateralcompartment in accordance with an example of the present application.

FIG. 5A is a cross-sectional view in a coronal plane of the tibialbearing component of FIG. 5 in accordance with an example of the presentapplication.

FIGS. 5B and 5C show a medial side of the tibial bearing component ofFIG. 5 including the medial compartment in accordance with an example ofthe present application.

FIGS. 6 and 6A show a lateral side of the tibial bearing component ofFIG. 5 in accordance with an example of the present application.

FIG. 7 shows a sizing chart for a family of tibial bearing componentsrelative to a family of femoral components, tibial components and tibialbearing components in accordance with an example of the presentapplication.

FIG. 8 is a plan view with contact areas between the femoral condylesand the tibial bearing component compartments shown at different degreesof flexion of the femoral component in accordance with an example of thepresent application.

DETAILED DESCRIPTION

The present application relates tibial prostheses, systems, and methods.The systems, for example, can include a tibial bearing component, and afemoral component.

FIG. 1 shows a schematic view of a proximal end 10 of a natural tibia 12according to an example of the present application. The natural tibia 12can include a lateral condyle 14 and a medial condyle 16.

The lateral condyle 14 can differ in shape and size relative to themedial condyle 16. FIG. 1 illustrates an amount of anterior-posteriortranslation of the lateral femoral condyle superimposed on the lateralcondyle 14 and a medial femoral condyle superimposed on the medialcondyle 16. Typically, the medial femoral condyle can experiencerelatively less anterior-posterior translation relative to the lateralfemoral condyle during flexion of the knee joint. This can result inexternal rotation and a medial pivoting motion for the natural femurduring femoral rollback. FIG. 1 provides an example where the medialfemoral condyle undergoes about 1.5 mm of anterior-posterior translationrelative to about 18 mm of anterior-posterior translation of the lateralfemoral condyle from about −5° to about 120° degrees of flexion.

In a total knee arthroplasty (referred to simply as a “TKA”) both of themedial and lateral condyles of the femur can be resected. Similarly, thetibia can be resected to remove the medial articular surface and thelateral articular surface using a cutting apparatus. Other portions ofthe knee, e.g., the intercondylar eminence, ACL can also be removed.Depending on the type of TKA, features such as the PCL can be spared orcan also be removed. Prostheses can be implanted on the femur and thetibia providing for the replaced articular surfaces. Although shown inreference to a TKA and corresponding implants, the techniques andmethods described herein are also applicable to other knee arthroplastyprocedures such as a partial knee arthroplasty (e.g., a unicompartmentalknee arthroplasty).

FIGS. 2 and 2A show an assembly 100 of a femoral component 110 with atibial bearing component 112 for a TKA according to one example. Asshown in FIG. 2, the femoral component 110 can include articularsurfaces 114 (only one is shown in FIG. 2) and proximal surfaces 116. Asshown in FIG. 2A, the articular surfaces 114 can include a medialcondyle 118 and a lateral condyle 120. The tibial bearing component 112can include an articular surface 122 and a distal surface 124. Thearticular surface 122 can include a medial compartment 126 and a lateralcompartment 128.

The femoral component 110 can comprise a femoral component that iscompatible with the Zimmer Biomet Persona® knee system manufactured byZimmer Biomet Holding, Inc. of Warsaw, Ind. The construction of thefemoral component is variously described in U.S. Pat. Nos. 8,858,643,9,072,607, 8,690,954, 8,764,838, 8,932,365 and United States ApplicationPublication No. 2012/0323336, the disclosures of which are incorporatedby reference in their entirety. Thus, the specific features of thefemoral component 110 will not be described in great detail herein.

As shown in the example of FIGS. 2 and 2A, the tibial bearing component112 is compatible with and configured for operable use with the femoralcomponent 110. In particular, the articular surface 122 of the tibialbearing component 112 can be configured to receive the articularsurfaces 114 of the femoral component 110 thereon and can be configuredto allow for movement of the femoral component 110 relative thereto in amanner that simulates the kinematics of a natural knee (e.g., allow forrollback of the femoral component 110 in flexion includinganterior-posterior translation).

The proximal surfaces 116 of the femoral component 110 can be configuredto receive and couple to resected distal surfaces of the femur. As shownin FIG. 2A, the articular surfaces 114 can comprise the medial condyle118 and the lateral condyle 120. The articular surface 122 can comprisethe medial compartment 126 and the lateral compartment 128. As shown inFIG. 2A, the medial compartment 126 and the lateral compartment 128 canbe configured for articulation with the medial condyle 118 and thelateral condyle 120 of the femoral component 110, respectively. Thearticular surface 122 can be arranged opposing the distal surface 124.The distal surface 124 can be shaped to interface with a proximalsurface of a tibial tray (not shown) that can be affixed to a resectedproximal surface of the tibia (not shown).

FIG. 3 shows a plan view of the articular surface 122 of the tibialbearing component 112 according to one example. Although the tibialbearing component 112 is shown having a cutout that allows acruciate-retaining configuration in FIG. 3 and other FIGURES herein, thetibial bearing component 112 can have other designs including aposterior stabilized configuration and/or an ultra-congruentconfiguration according to other examples that are not intended forcruciate-retaining configuration.

Various aspects of the articular surface 122 discussed in further detailsubsequently allow the tibial bearing component 112 to provide a desiredstability to the medial condyle 118 (FIG. 2A) of the femoral component110 (FIG. 2A) while additionally providing a desired mobility to thelateral condyle 120 (FIG. 2A) of the femoral component 110 (FIG. 2A).FIGS. 3 and 4 illustrate and are accompanied by discussion of thedesired stable medial condyle and mobile lateral condyle in terms oflaxity ranges. FIGS. 5 to 6A and 8 illustrate and are accompanied bydiscussion of various features of the configuration of the medial andlateral bearing compartments 126, 128 that can improve stabilization ofthe medial condyle and additionally can improve mobility of the lateralcondyle during flexion. A sizing scheme is presented in FIG. 7 forsizing various of the tibial bearing components and femoral componentsof the respective families in a manner such that they can be used incombination to better achieve the desired stable medial condyle andmobile lateral condyle.

In FIG. 3, the medial compartment 126 and the lateral compartment 128are illustrated having different average anterior-posterior laxity from0° to 120° flexion as shown by circles 130L and 130M. As shown in thegraphs of FIGS. 4A to 4D, the laxity can comprise a degree of change inthe anterior-posterior position of the lateral condyle and the medialcondyle plotted against degrees of flexion of the femoral component.Graphs 150 of FIG. 4A and 152 of FIG. 4B, are plots of the lateralcondyle 118 and the medial condyle 120, respectively, for a cruciateretained configuration of the tibial bearing component 112 of FIG. 3. Asexhibited by the graph 152 of FIG. 4B the medial condyle 118 (FIG. 2A)when used with the tibial component 112 can be relatively morestabilized (has a tighter laxity range as indicated by area 154 of FIG.4B) when measured against a commercially available knee component design(as indicated by area 156 of FIG. 4B), a cruciate retained configurationof the Persona® knee system, manufactured by Zimmer Biomet Holdings,Inc., of Warsaw, Ind. Similarly, graph 150 of FIG. 4A shows the lateralcondyle 120 (FIG. 2A) when used with the tibial bearing component 112can have more have more mobility (has a larger laxity range as indicatedby area 158 of FIG. 4A) when measured against the same commerciallyavailable Persona® knee system (as indicated by area 159 of FIG. 4A).

Graphs 160 of FIG. 4C and 162 of FIG. 4D are plots of the lateralcondyle and the medial condyle, respectively, for a cruciate sacrificedconfiguration of the tibial bearing component as described herein. Asexhibited by the graph 162 of FIG. 4D, the medial condyle of the femoralcomponent can be relatively more stabilized (has a tighter laxity rangeas indicated by area 166 of FIG. 4D) when measured against acommercially available knee component design (as indicated by area 164of FIG. 4D), a cruciate sacrificed configuration of the Persona® kneesystem, manufactured by Zimmer Biomet Holdings, Inc., of Warsaw, Ind.Similarly, graph 160 of FIG. 4C shows the lateral femoral condyle canhave relatively more mobility (has a larger laxity range as indicated byarea 168 of FIG. 4C) when measured against the same commerciallyavailable Persona® knee system (as indicated by area 170 of FIG. 4C).

FIGS. 5, 5A, 5B, and 5C are views of a tibial bearing component 212according to an example of the present application. Tibial bearingcomponent 212 can be substantially similar to tibial bearing component112 previously described herein and adds further detail regardingaspects of the construction of the tibial bearing component. As shown inFIG. 5, the tibial bearing component 212 can include an articularsurface 214, a periphery 216, a posterior cutout 218 and an anteriorrelief space 219. The articular surface 214 can include a medialcompartment 220, a lateral compartment 222 and an intercondylar eminence224.

As previously described, the articular surface 214 can be contacted bythe condyles (not shown) of a femoral component when operably assembledin the knee. The condyles of the femoral component can contact themedial and lateral compartments 220, 222. More particularly, the medialcompartment 220 and the lateral compartment 222 can be configured (e.g.are dish shaped) for articulation with the medial condyle and thelateral condyle of the femoral component, respectively (as shown in FIG.2A). The articular surface 214 (sometimes referred to as the proximalsurface herein) can be generally opposed by a distal surface 215 asshown in FIGS. 5A and 5C. The periphery 216 can comprise sidewallsconnecting with the distal surface 215 and the articular surface 214.The medial compartment 220 can differ in configuration from the lateralcompartment 222 as will be explained in further detail subsequently. Forexample, the medial compartment 220 can have a different size and shaperelative to the lateral compartment 222. For example, theanterior-posterior curvature of the lateral compartment 222 can differfrom that of the medial compartment 220. Similarly, as shown in FIG. 5Cand FIG. 6A, a medial-lateral curvature of the lateral compartment 222can differ from a medial-lateral curvature of the medial compartment220.

As shown in the example of FIG. 5, the lateral compartment 222 can havea lateral articular track 226 having a lateral anterior-posterior extentLAP. The lateral articular track 226 can comprise a plurality ofdistal-most points along the proximal surface 214 of the lateralcompartment 222 that are contacted by the lateral femoral condyle duringrollback of the femoral component. Similarly, the medial compartment 220can have a medial articular track 228 having a medial anterior-posteriorextent MAP that differs from the lateral anterior-posterior extent LAP.The medial articular track 228 can comprise a plurality of distal-mostpoints along the proximal surface 214 of the medial compartment 220 thatare contacted by the medial femoral condyle during rollback of thefemoral component.

As shown in FIGS. 5, 6 and 6A, in one example the lateral compartment222 can have an anterior portion 230 and a posterior portion 232. Theanterior portion 230 can define the lateral articular track 226 as anominally straight line 231 when projected onto a transverse plane ofthe tibial bearing component 212. The posterior portion 232 can definethe lateral articular track 226 as a curved line 233 toward the medialcompartment 220 when projected onto the transverse plane of the tibialbearing component 212.

In contrast, the medial articular track 228 can define a nominallystraight line 235 when projected onto the transverse plane of the tibialbearing component 212, and the medial articular track 228 defined by themedial compartment 220 can be comprised of a uniform single curve havingonly a single sagittal radius R as shown in FIG. 5C. The nominallystraight line that can be defined by the medial articular track 228 canbe substantially parallel to the nominally straight line defined by theanterior portion 230 of the lateral articular track 226 in some cases.

For convenience, the present discussion refers to points, tracks orlines of contact between tibial bearing component 212 and the femoralcomponent along the articular tracks 226, 228. However, it is of courseappreciated that each potential point or line of contact (i.e., any ofthe points along one of the articular tracks 226, 228) is not truly apoint or line, but rather an area of contact as illustrated in FIG. 8.These areas of contact may be relatively larger or smaller depending onvarious factors, such as prosthesis materials, the amount of pressureapplied at the interface between tibial bearing component 212 andfemoral component, relative shapes of the tibial bearing component 212relative to the femoral component, and the like. Moreover, it isappreciated that some of the factors affecting the size of the contactarea may change dynamically during prosthesis use, such as the amount ofapplied pressure at the femoral/tibial interface during walking,climbing stairs or crouching, for example. For purposes of the presentdiscussion, a contact point may be taken as the point at the geometriccenter of the area of contact. The geometric center, in turn, refers tothe intersection of all straight lines that divide a given area into twoparts of equal moment about each respective line. Stated another way, ageometric center may be said to be the average (i.e., arithmetic mean)of all points of the given area. Similarly, a line or track is thecentral line of contact passing through and bisecting an elongate areaof contact.

Both the medial compartment 220 and the lateral compartment 222 canincluded dwell points 234 and 236. The dwell points 234 and 236 cancomprise distal-most points along the medial articular track 228 and thelateral articular track 226, respectively. As shown in TABLES 1 below,the medial compartment 220 can be configured to have the medial dwellpoint 234 a distance between about 61% and about 66% of a totalanterior-posterior extent T of the tibial bearing component 212 asmeasured from an anterior most point A of the tibial bearing component212 to a posterior most point P of the tibial bearing component 212.

TABLE 1 With Anterior Slope % of A/P Dwell point to 0° Name overallMedial A/P MC 1-2/AB 61% 3-4/AB 61% 4-5/CD 64% 6-7/CD 62% 8-9/CD 61%4-5/EF 66% 6-7/EF 64% 8-11/EF 63% 8-11/GH 66% 12/GH 65% 12/J 64%

TABLE 2 With Anterior Slope % of A/P Dwell point to 0° Name overallLateral A/P MC 1-2/AB 69% 3-4/AB 68% 4-5/CD 69% 6-7/CD 67% 8-9/CD 65%4-5/EF 69% 6-7/EF 68% 8-11/EF 66% 8-11/GH 67% 12/GH 67% 12/J 65%

As shown in TABLE 2, the lateral compartment 222 can be configured tohave the lateral dwell point 236 a distance between about 65% and about69% of the total anterior-posterior extent T of the tibial bearingcomponent 212 as measured from the anterior most point A to theposterior most point P of the tibial bearing component 212.

As shown in FIG. 5, the posterior cutout 218 is sized and positioned toaccommodate a posterior cruciate ligament upon implantation of tibialbearing component 212. The intercondylar eminence 224 can comprise anintercondylar ridge of the articular surface 214 that can be disposedbetween the medial and lateral compartments 220, 222. The intercondylareminence 224 can extend generally anterior-posterior from the posteriorcutout 218 to the anterior relief space 219. Thus, the intercondylarridge defined by the intercondylar eminence 224 can be disposed betweenthe medial and lateral dished medial and lateral compartments 220, 222and occupies the available anterior-posterior space therebetween.

FIG. 5A shows a cross-section through the bearing component in a coronalplane and illustrates the medial-lateral radii R₁ and R₂ of each of themedial compartment 220 and the lateral compartment 222. These radii canbe the same for the medial and lateral or differ according to variousexamples. FIG. 5A additionally illustrates the distal surface 215, theperiphery 216, and the intercondylar eminence 224. As shown in FIG. 5A,the periphery 216 can be shaped to mate with corresponding features of asidewall of a tibial tray (now shown) such as to create an interferencefit.

FIGS. 5B and 5C show a medial side of the tibial bearing component 212in further detail including the medial compartment 220. As shown in FIG.5C, the tibial bearing component 212 can have an anterior lip height 240of between about 9 mm and about 13 mm as measured from the dwell point234 to a proximal most point of the medial compartment 220. FIG. 5Cshows the medial compartment 220 in cross-section along a sagittal planeand shows the medial compartment 220 can have a single sagittal radiusR_(SM).

FIGS. 6 and 6A show a lateral side of the tibial bearing component 212in further detail including the lateral compartment 222 from a differentperspective than those of FIGS. 5 to 5C. FIG. 6 shows the lateralcompartment 222 can have an anterior portion 230 and a posterior portion232. Recall from FIG. 5, the anterior portion 230 can define the lateralarticular track 226 as a nominally straight line 231 when projected ontoa transverse plane of the tibial bearing component 212. The posteriorportion 232 can define the lateral articular track 226 as a curved line233 toward the medial compartment 220 when projected onto the transverseplane of the tibial bearing component 212. FIG. 6A shows the lateralcompartment 222 in cross-section and shows the lateral compartment 222can have a first sagittal radius R_(SL1) in the anterior portion and asecond sagittal radius R_(SL2) in the posterior portion with thetransition between the first sagittal radius R_(SL1) and the secondsagittal radius R_(SL2) indicated by the line P.

The tibial bearing components and the femoral components describedherein can each be available as a family of tibial bearing componentsand a family of femoral components, respectively. The family of tibialbearing components can be of a same design class (e.g., be shaped to becruciate regaining) and can have different stock sizes (e.g., from asmall stature size A to a largest size J). Similarly, the family offemoral bearing components can be a same design class (e.g., be shapedto articulate with a cruciate retaining configured tibial bearingcomponent) and can have different stock sizes (e.g., from a smallstature size 1 to a largest size 12).

FIG. 7 shows a sizing chart for the family of tibial components 312relative to the family of femoral components 314. More particularly, thesizing chart shows the family of femoral components 314 can have atleast twelve different stock sizes 1 to 12. As previously discussed andillustrated, each femoral component can be of a same design class andcan include a medial condyle and a lateral condyle. The family of tibialcomponents 312 can have at least nine different stock sizes A to J. Asshown in FIG. 7, the family of tibial bearing components 313 can beconfigured such that eleven stock sizes exist and that combinations ofthe at least nine different stock sizes of the family of tibialcomponents are compatible for operable use (e.g. to facilitate a desiredarticulation similar to that of a natural knee) with the at least twelvedifferent stock sizes of the family of femoral components 314. FIG. 7also illustrates that nine out of the eleven different stock sizes oftibial bearing components are compatible with no more than two of thetwelve stock sizes of femoral components. According to further examples,ten of the at least twelve different stock sizes of the family offemoral components 314 can be compatible for operable use with eight ofthe at least nine different stock sizes of the family of tibial bearingcomponents 313. Additionally, eight of the at least twelve differentstock sizes of the family of femoral components 314 can be compatiblefor operable use with six of the at least nine different stock sizes ofthe family of tibial bearing components 313. According to furtherexamples, no more than four of the at least twelve different stock sizesof the family of femoral components can be compatible for operable usewith two of the at least twelve different stock sizes of the tibialbearing components.

This overlapping sizing and the provision of many different compatiblesizes can have benefits including providing for increased stability ofthe medial condyle of the femoral component. For example, by having afamily of tibial bearing components that can include at least elevendifferent stock sizes and a family of femoral components that caninclude at least twelve different stock sizes with twenty four differentpossible operable combinations, in a worst case scenario a medialconformity between the femoral component and the tibial bearingcomponent in extension can have a conformity ratio of 1.1:1, and overhalf (54%) of the operable combinations between the sizes of the familyof tibial bearing components and the sizes of the family of femoralcomponents can have a conformity ratio of 1:1. “Conformity,” (alsoreferred to as “congruence” or “congruence ratio” in the context of kneeprostheses, refers to the similarity of curvature between the convexfemoral condyles and the correspondingly concave tibial articularcompartments in the sagittal plane. Thus, the conformity ratio cancomprise a ratio of the similarity between a sagittal radius of themedial tibial bearing compartment and a sagittal radius of the medialfemoral condyle.

Furthermore, having overlapping sizing and the provision of manydifferent compatible sizes (alone and/or in addition to shaping thecompartments to better conform with the condyles using aspectspreviously discussed) can provide for an increased contact area betweenthe medial condyle of the femoral component and the medial compartmentof the tibial bearing component. As a result, the femoral component canhave greater stability with respect to the medial condyle. Examples ofsuch contact areas 402 (medial compartment contact area) and 404(lateral compartment contact area) are illustrated in FIG. 8, whichshows an articular surface 414 of a tibial bearing component 412contacted at different flexion angles by a femoral component. TABLE 3shows combinations of differently sized femoral and tibial bearingcomponents from families of tibial bearing components and femoralcomponents can achieve an arrangement where a minimum 31% of an overallsurface area of the medial compartment can be contacted with the femoralcomponent in 0° flexion and a minimum 13% of the overall surface area ofthe medial compartment can be contacted with the femoral component in45° flexion.

TABLE 3 MC Femur 0° Flexion 45° Flexion Size Size Medial Lateral Medial1-2/AB 2 NAR 51% 31% 58% 6-7/CD  7 STD 62% 36% 48% 8-9/CD  9 STD 63% 40%14% 8-11/EF 11 STD 61% 36% 33% 8-11/GH  8 STD 31% 25% 13% 12/GH 12 STD55% 32% 59% Min 31% 25% 13% Max 63% 40% 59% Average 54% 33% 38%According to the example shown in TABLE 3, combinations of differentlysized femoral and tibial bearing components can be configured such thatbetween about 31% and about 63% of an overall surface area of the medialcompartment is contacted by the medial condyle of the femoral componentwith the femoral component in 0° flexion. Put another way, the medialcompartment can be configured relative to the medial condyle to havebetween about 31% and about 63% of an overall surface area thereofcontacted by the medial condyle of the femoral component with thefemoral component in 0° flexion.

ADDITIONAL NOTES

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” Such examples can include elements in addition tothose shown or described. However, the present inventors alsocontemplate examples in which only those elements shown or described areprovided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) can be used in combination with each other. Otherexamples can be used, such as by one of ordinary skill in the art uponreviewing the above description. The Abstract is provided to comply with37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain the natureof the technical disclosure. It is submitted with the understanding thatit will not be used to interpret or limit the scope or meaning of theclaims. Also, in the above detailed description, various features can begrouped together to streamline the disclosure. This should not beinterpreted as intending that an unclaimed disclosed feature isessential to any claim. Rather, inventive subject matter can lie in lessthan all features of a particular disclosed example. Thus, the followingclaims are hereby incorporated into the detailed description as examplesor embodiments, with each claim standing on its own as a separateexample, and it is contemplated that such examples can be combined witheach other in various combinations or permutations. The scope of theinvention should be determined with reference to the appended claims,along with the full scope of equivalents to which such claims areentitled.

The claimed invention is:
 1. A tibial bearing component for articulationwith a medial condyle and a lateral condyle of a femoral component in aknee replacement procedure, the tibial bearing component comprising: adistal surface; and an articular surface opposing the distal surface,the articular surface including a medial compartment and a lateralcompartment configured for articulation with the medial condyle and thelateral condyle of the femoral component, respectively; the lateralcompartment having a lateral articular track with a lateralanterior-posterior extent, the lateral articular track comprising aplurality of distal-most points along a proximal surface of the lateralcompartment that are contacted by the lateral condyle during rollback ofthe femoral component; the medial compartment differing in configurationfrom the lateral compartment and having an anterior lip height asmeasured from a distal-most point of the articular surface to aproximal-most point of the medial compartment of between 9 mm and 13 mm,wherein the medial compartment is configured relative to the medialcondyle to have between 31% and 63% of an overall surface area thereofcontacted by the medial condyle of the femoral component with thefemoral component in 0° flexion.
 2. The tibial bearing component ofclaim 1, wherein the lateral compartment has an anterior portion and aposterior portion, the anterior portion defines the lateral articulartrack as a nominally straight line when projected onto a transverseplane of the tibial bearing component, the posterior portion defines thelateral articular track with a curved line toward the medial compartmentwhen projected onto the transverse plane of the tibial bearingcomponent.
 3. The tibial bearing component of claim 2, wherein thelateral compartment has a first sagittal radius in the anterior portionand a second sagittal radius in the posterior portion.
 4. The tibialbearing component of claim 1, wherein the medial compartment has amedial articular track with a medial anterior-posterior extent thatdiffers from the lateral anterior-posterior extent, the medial articulartrack comprising a plurality of distal-most points along a proximalsurface of the medial compartment that are contacted by the medialfemoral condyle during rollback of the femoral component, wherein themedial compartment defines the medial articular track as a nominallystraight line when projected onto the transverse plane of the bearingcomponent and the medial articular track has a single sagittal radius.5. The tibial bearing component of claim 4, wherein the medialcompartment is configured to have a medial dwell point a distancebetween 61% and 66% of a total anterior-posterior extent of the tibialbearing component as measured from an anterior most point to a posteriormost point of the tibial bearing component.
 6. The tibial bearingcomponent of claim 1, wherein the lateral compartment is configured tohave a lateral dwell point a distance between 65% and 69% of a totalanterior-posterior extent of the tibial bearing component as measuredfrom an anterior most point to a posterior most point of the tibialbearing component.
 7. The tibial bearing component of claim 1, whereinthe medial compartment is configured to have between a 1:1 congruenceratio and a 1.1:1 congruence ratio with the medial condyle, thecongruence ratio comprising a ratio of the similarity between a sagittalradius of the medial compartment and a sagittal radius of the medialcondyle.
 8. A tibial bearing component for articulation with a medialcondyle and a lateral condyle of a femoral component in a kneereplacement procedure, the tibial bearing component comprising: a distalsurface; and an articular surface opposing the distal surface, thearticular surface including a medial compartment and a lateralcompartment configured for articulation with the medial condyle and thelateral condyle of the femoral component, respectively; the lateralcompartment configured to have a lateral dwell point a distance between65% and 69% of a total anterior-posterior extent of the tibial bearingcomponent as measured from an anterior most point to a posterior mostpoint of the tibial bearing component; wherein the medial femoralcondyle undergoes 3 mm of anterior-posterior translation relative to 11mm of anterior-posterior translation of the lateral femoral condyle from0° to 120° degrees of flexion.
 9. The tibial bearing component of claim8, wherein the medial compartment differs in configuration from thelateral compartment and has an anterior lip height of between 9 mm and13 mm as measured from a distal-most point of the articular surface to aproximal-most point of the medial compartment.
 10. The tibial bearingcomponent of claim 8, wherein the lateral compartment has a lateralarticular track with a lateral anterior-posterior extent, the lateralarticular track comprising a plurality of distal-most points along aproximal surface of the lateral compartment that are contacted by thelateral condyle during rollback of the femoral component, and whereinthe lateral compartment has an anterior portion and a posterior portion,the anterior portion defines the lateral articular track as a nominallystraight line when projected onto a transverse plane of the tibialbearing component, the posterior portion defines the lateral articulartrack with a curved line toward the medial compartment when projectedonto the transverse plane of the tibial bearing component.
 11. Thetibial bearing component of claim 10, wherein the lateral compartmenthas a first sagittal radius in the anterior portion and a secondsagittal radius in the posterior portion.
 12. A tibial bearing componentfor articulation with a medial condyle and a lateral condyle of afemoral component in a knee replacement procedure, the tibial bearingcomponent comprising: a distal surface; and an articular surfaceopposing the distal surface, the articular surface including a medialcompartment and a lateral compartment configured for articulation withthe medial condyle and the lateral condyle of the femoral component,respectively; wherein the medial compartment is configured relative tothe medial condyle to have between 31% and 63% of an overall surfacearea thereof contacted by the medial condyle of the femoral componentwith the femoral component in 0° flexion.
 13. The tibial bearingcomponent of claim 12, wherein the lateral compartment configured tohave a lateral dwell point a distance between 65% and 69% of a totalanterior-posterior extent of the tibial bearing component as measuredfrom an anterior most point to a posterior most point of the tibialbearing component.
 14. The tibial bearing component of claim 13, whereinthe medial compartment is configured to have a medial dwell point adistance between 61% and 66% of a total anterior-posterior extent of thetibial bearing component as measured from an anterior most point to aposterior most point of the tibial bearing component.
 15. The tibialbearing component of claim 12, wherein the medial compartment differs inconfiguration from the lateral compartment and has an anterior lipheight of between 9 mm and 13 mm as measured from a distal-most point ofthe articular surface to a proximal-most point of the medialcompartment.
 16. The tibial bearing component of claim 12, wherein themedial compartment is configured to have between a 1:1 congruence ratioand a 1.1:1 congruence ratio with the medial condyle, the congruenceratio comprising a ratio of the similarity between a sagittal radius ofthe medial compartment and a sagittal radius of the medial condyle. 17.The tibial bearing component of claim 12, wherein the lateralcompartment has a lateral articular track with a lateralanterior-posterior extent, the lateral articular track comprising aplurality of distal-most points along a proximal surface of the lateralcompartment that are contacted by the lateral condyle during rollback ofthe femoral component, and wherein the lateral compartment has ananterior portion and a posterior portion, the anterior portion definesthe lateral articular track as a nominally straight line when projectedonto a transverse plane of the tibial bearing component, the posteriorportion defines the lateral articular track with a curved line towardthe medial compartment when projected onto the transverse plane of thetibial bearing component.
 18. The tibial bearing component of claim 17,wherein the lateral compartment has a first sagittal radius in theanterior portion and a second sagittal radius in the posterior portion.